Celebrity website TMZ.com said the couple, who reunited earlier this year, are planning a New Year's Eve wedding.

Harris was Playboy magazine's Miss December 2009 and appeared on the July 2011 cover of the adult magazine with a "runaway bride" sticker covering her bottom half.

In what was described at the time only as a "change of heart," Harris dumped the magazine mogul and left his Playboy Mansion five days before a lavish June 2011 wedding before 300 guests.

This time around, the couple are playing it low-key, staying mum on their busy Twitter accounts with Hefner's spokeswoman declining to confirm or deny their plans.

Hefner, founder of the Playboy adult entertainment empire, has been married twice before. He and his second wife Kimberley Conrad, also a former Playmate, divorced in 2010 after a lengthy separation. His first marriage to Mildred Williams ended in divorce in 1959. He has two children from each marriage.